Work machines, such as excavators, backhoes, and other digging machines, may include implement arms having a distally located work implement. The separate components making up the implement arm may be coupled by pin connections forming a series of implement arm joints. The pin connections are formed by positioning a pin within aligned holes in adjacent components of the implement arm. The pin connections allow the adjacent components of the implement arm to pivot with respect to one another and together allow the implement arm to move through its full working motion.
Some work machines are equipped with computer systems capable of computing the position of the implement arm during operation. In particular, such computer systems may inform the operator of the vertical depth or horizontal distance from a reference point. The known computer systems typically input values received from sensors coupled to the implement arm into a simplified kinematics model of the implement arm to determine its position. For example, U.S. Pat. No. 6,185,493 to Skinner et al. discloses a system for controlling a bucket position of a loader. The Skinner et al. system includes position sensors that determine the vertical position of the boom of the implement arm and the pivotal position of the bucket. With these sensed values, the approximate position of the bucket can be calculated throughout its movement.
However, several sources of error may affect the accuracy of the implement arm position determined with existing computer systems. For example, if any part of the implement arm deviates from a simplified kinematics model, there will be a discrepancy between the actual position and the calculated position of the implement arm. One such deviation is introduced at the pin connections of the implement arm joints. The pins of the pin connections are typically loosely fit into the aligned holes in the implement arm components, thus forming pin clearances at the implement arm joints. These pin clearances allow the components of the implement arm to shift during operation. This shifting of the implement arm components is an aspect not taken into account in known implement arm position detecting systems.
This disclosure is directed toward overcoming one or more of the problems or disadvantages associated with the prior art.